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Thread: Altec A7 refurbish

  1. #16
    Senior Member sbjacob's Avatar
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    Quote Originally Posted by teddy.edwards1 View Post
    hey, i was just wondering how you crossed over your subs and at what frequency?
    do you have them as additional to the 515's low end, or is there a HPF on the 515's?
    I made 4 LAB Subs and also 4 Tuba 30's (not my pics) which are a bit impractical actually, but go very low and smooth.

    tom
    Hi I'm pleased with the sound I haven't hooked up any subs yet I have 4 Bose 302 bandpass subs not real good but I use them on small gigs with 802-II's it's a nice portable system. I was looking at the Danley DTS-10 sub they sell kits for around $1200 and have talked to some that have them and they are very happy "True Thunder" was what was said to me by a fellow Forum member.I tlked to GPA and the recomended there 515-G8 woofer for the A7 but I'm using the Eminence Kappa C's very similar specs to the GPA 515-G8. The Kappa C specs on the Eminence website are the same as the 8 ohm Kappa A's not correct Parts Express has the correct specs not alot of difference . http://www.danleysoundlabs.com/produ...y-subs/dts-10/

  2. #17
    Senior Member louped garouv's Avatar
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    Quote Originally Posted by teddy.edwards1 View Post
    hey, i was just wondering how you crossed over your subs and at what frequency?
    do you have them as additional to the 515's low end, or is there a HPF on the 515's?
    I made 4 LAB Subs and also 4 Tuba 30's (not my pics) which are a bit impractical actually, but go very low and smooth.

    tom
    Hi Tom,
    At the time, I was using an RLA x2000 xover..

    The 515s were 25hz to 800hz
    Subs ran 20hz to 100hz

  3. #18
    Senior Member sbjacob's Avatar
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    Quote Originally Posted by louped garouv View Post
    Hi Tom,
    At the time, I was using an RLA x2000 xover..

    The 515s were 25hz to 800hz

    Subs ran 20hz to 100hz
    Any one add fuses to the 2404 tweeters if so how large I'm crossing my 2404's at 6000Hz 4th order Linkwitz passive? Thanks

  4. #19
    Senior Member Baron030's Avatar
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    Rather than fuses, what about using JBL SK3 Crossover Protection Bulbs instead.

    Baron030

  5. #20
    Senior Member sbjacob's Avatar
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    Quote Originally Posted by Baron030 View Post
    Rather than fuses, what about using JBL SK3 Crossover Protection Bulbs instead.

    Baron030
    Didn't know about these I ordered a few I assume networking instruction come with them but just in case they don't do you add them to the + input on the 2404's?

  6. #21
    Senior Member Baron030's Avatar
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    If you had already ordered a few of the SK3 bulbs, I donít think they come with instructions on how to use them in your own special application. But, donít fret about it too much because JBL is using them in a lot of different crossover networks. So, I suspect that one of the following will turn up a schematic that you can copy.

    JBL MR Series, JBL MR800 Series, JBL MR900 Series, JBL SF Series, JBL Cab Series, JBL TR Series, JBL Sound Factor Series, JBL Control Series, JBL MP Series, JBL M-Pro Series, JBL Eon Non-Powered Series, JRX Series.

    The SK3 bulb does more that than act as a just a fuse. Because the tungsten filamentís resistance varies so greatly with temperature, it can act more like a compressor preventing damage to the driver without blowing like a regular fuse. In the TR125 example below, the two SK3 bulbs and the 16 ohm resistor form a series attenuator for the HF driver. At low power levels the bulb resistance is low and there is no compressor effect. But at excessively high power levels the bulbs light up and their resistance increases, which will reduce the power going to the HF driver. And at catastrophic overload power levels the bulbs will burn out, leaving only the 16 ohm resistor to supply a very limited amount of power to the HF driver until the SK3 bulbs can be replaced. I suspect that in other networks, R1 value maybe different depending on the HF driverís impedance and power handling characteristics.

    Baron030
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  7. #22
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    caps

    Quote Originally Posted by sbjacob View Post
    Didn't know about these I ordered a few I assume networking instruction come with them but just in case they don't do you add them to the + input on the 2404's?
    you can also use protection capacitors...
    The JBL/UREI - 525 active crossover manual has some frequency/capacitance tables
    UREI 525

    thanks
    tom

  8. #23
    Senior Member sbjacob's Avatar
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    Quote Originally Posted by teddy.edwards1 View Post
    you can also use protection capacitors...
    The JBL/UREI - 525 active crossover manual has some frequency/capacitance tables
    UREI 525

    thanks
    tom
    I'm using a Ashly XR1001 active and I built a 4th order Linkwitz for the JBL2404's so I don't believe these bulbs will work they are for JBL networks I have stated a few posts back I was using a active with the passive I built.

  9. #24
    Senior Member Baron030's Avatar
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    Hi SBJACOB
    I am not suggesting that you replace your existing passive crossover networks. Just modify them to include SK3 bulbs if you are so concerned about protecting your drivers. Now if I understand your system correctly. You have a XR1001 electronic network between the woofers and the midrange horns. The BGW750C amp feeds the woofers and the BGW250D feeds both the midrange and the 2404s. And the 6000Hz passive network slits the signal between the midrange and 2404s. In the schematic below, what I donít know is, what are the correct R1 and R2 values for your application. But, this is something that can be derived from studying other JBL networks that have SK3 bulbs. Now, if the 2404H driver has the same power handing as a 2412H driver, then the appropriate R1 value would be a 16 ohm 10 watt resistor. Otherwise, then a different value would be needed. Actually, for a home audio system I donít see the need to fuses or SK3 protection bulbs. But, in a pro sound reinforcement system where microphone feedback could route several hundred watts into a HF driver the SK3 bulbs seem like a really good idea.
    Baron030
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  10. #25
    Senior Member sbjacob's Avatar
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    Quote Originally Posted by Baron030 View Post
    Hi SBJACOB
    I am not suggesting that you replace your existing passive crossover networks. Just modify them to include SK3 bulbs if you are so concerned about protecting your drivers. Now if I understand your system correctly. You have a XR1001 electronic network between the woofers and the midrange horns. The BGW750C amp feeds the woofers and the BGW250D feeds both the midrange and the 2404s. And the 6000Hz passive network slits the signal between the midrange and 2404s. In the schematic below, what I donít know is, what are the correct R1 and R2 values for your application. But, this is something that can be derived from studying other JBL networks that have SK3 bulbs. Now, if the 2404H driver has the same power handing as a 2412H driver, then the appropriate R1 value would be a 16 ohm 10 watt resistor. Otherwise, then a different value would be needed. Actually, for a home audio system I donít see the need to fuses or SK3 protection bulbs. But, in a pro sound reinforcement system where microphone feedback could route several hundred watts into a HF driver the SK3 bulbs seem like a really good idea.
    Baron030
    Attachment 56122
    I didn't take it that way wasn't sure if you had seen the previous posts on the setup and yes that is the way I have it set up sounds fantastic I added a BBE sonic max. and it really helps the low-mid slam the Eminence Kappa C's are keepers can't imagine the GPA 515's would sound better the woofer parameters are almost the same between the two of them. I think I'll be ok without any protection the BGW 250D is about 100 watts and has protective circuitry so I'll leave it be for the time being as they add a very nice up HF to the sound.

  11. #26
    Senior Member vernb's Avatar
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    Quote Originally Posted by sbjacob View Post
    I pick up a few A7 cabinets in good condition and have repainted them I took the small crossover cover off the back and went to Ace and they scanned it to match the paint worked very nice I also ordered new logos off Ebay for them very nice for $18. for 4 . I have a pair of 511B horns and 909-16 drivers just need woofers I had a pair of Eminence Kappa C so I put them in just for kicks and used a Ashly XR1001 active with a BGW 750C on the LF and a BGW 250D on the HF had to turn the HF gain way down as it was over powering the LF any suggestions on woofers is the 416 the way to go on these
    I went to GPA website and noticed the 515 LF specs are close to the Kappa C 4 ohm Vas is 11.7 vs 16.6 the Qes .25 vs .26 Qts .25 vs .25 Qms 10.14 vs 11.6 FS 31Hz vs 27Hz
    Very nice job. I just got myselt a pair yesterday, but they need a paintjob aswell. Which is the right Altec grey for VOTT?
    Best regards
    Vern

  12. #27
    Senior Member sbjacob's Avatar
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    Quote Originally Posted by vernb View Post
    Very nice job. I just got myselt a pair yesterday, but they need a paintjob aswell. Which is the right Altec grey for VOTT?Best regardsVern
    Hi I went to Ace and they scanned the crossover panel cover to match the paint and mixed up some for me a perfect match. Anyway I have just finished putting internal bracing in the cabinets and I'm pleased to say the bass is much tighter. I tied the two bottom sides together with a 2"x4" and added acoustic foam on the top horns space also added another 3/4" board to the back of the ports to stiffen them up honestly these cabinets stock are lacking.I also took the old grey cloth out and replaced it with new black Duracrest cloth.Name:  IMG_0540.jpg
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